In the past, guidelines for flying after diving were quite varied. For example, a single no-stop dive, the U.S. Navy recommended a 2-hour surface interval time (SIT), DAN recommended 12 hours SIT, and the U.S. Air Force recommended 24 hours SIT.

A focal point in DANís research is repetitive dives across the range of depths common in recreational diving, using a series of different surface intervals. Researchers analyze experimental data to develop a model for estimating decompression risk at the Center for Hyperbaric Medicine and Environmental Physiology at Duke University Medical Center.

For this study, more than 500 subjects participated in the experiments at the Center for Hyperbaric Medicine and Environmental Physiology at Duke University Medical Center. Dives spanned the typical recreational depth range: 40 fsw (feet of seawater), 60 fsw, and 100 fsw, and dive times were near the recommended recreational limits. Researchers tested both single and repetitive dives.

Following the dives, participants took a four-hour flight at a simulated altitude of 8,000 feet in the chamber. This is the maximum cabin altitude allowed by the Federal Aviation Administration for pressurized commercial aircraft.

The objective of the study was to estimate the relationship between the pre-flight surface interval and DCI incidence for each dive series. A pre-flight surface interval was accepted or rejected within the study based upon the number of DCI incidents and total exposures. Acceptance and rejection rules were chosen to allow mild DCI but limit more serious DCI. The Duke Institutional Review Board of Duke Medical Center approved these rules.

All subjects were dry, and at rest, throughout the dives and flight. The subjects were certified recreational divers who went through medical history reviews and physical examinations by a DAN diving physician. In addition, they had to be at least 18 years old, not pregnant if female, and body composition must be within 40% of their ideal weight. Subjects were eligible for more than one study as the profiles changed, but a subject could participate in only one profile series.